SAE J418_199905

This classification for grain size comprises three sets of comparison charts to be used for determining grain size. These charts are presented in three categories as follows: Plate I – Untwinned grains (flat etch) Plate II – Twinned grains (flat etch) Plate IV – Austenite grains in steel (McQuaid-Ehn test or other test) Table 1 lists a number of materials and the comparison charts that are suggested for use in estimating their grain size by the comparison method. NOTE—The suggestions in Table 1 are based upon the customary practices in industry. For specimens prepared according to special techniques, the appropriate comparison chart should be selected on a structural appearance basis as described in the Scope.